Recent evidence suggests that linoleic acid 18:2 (omega-6) alone may be insufficient to fully satisfy essential fatty acid (EFA) nutrition during late fetal and early postnatal life. A possible need for omega-3 fatty acids (omega-3) is suggested by the accretion rates of omega-3 derivatives in the developing fetus, the altered fatty acid pattern and abnormal visual and mental function observed on an alpha-linolenic acid (18:3 omega-3)-free parenteral fat solution in the human; and evidence of abnormal visual acuity threshold of newborn Rhesus monkeys fed a linolenic acid-poor diet. Most milk formula for prematures, as compared to human milk, are lower in oleic acid, higher in linoleic, have little alpha-linolenic acid and virtually no omega-3 fatty acids of greater than 18 carbon chain length. This study will evaluate the potential effects of omega-3 fatty acid deficiency in the VLBW human neonate by studying functional indicators of deficiency. We will measure eye and cortical response to light stimulation, visual acuity, plasma and RBC membrane fatty acid composition. Four groups of 20 VLBW (<1500 AGA) each will be studied from day 10 through day 45 or discharge from the nursery; follow up studies will be conducted at 4 months adjusted postnatal age. Group A will receive preterm human milk; group B, artificial formula with a 18:2omega-6/18:3omega-3=121; Group C, a formula with an omega-6/omega-3=12 similar to that in human milk and Group D, a formula that will include long chain omega-3 fatty acids in the proportion found in human milk. Blood samples and cheek cells will be obtained on days 10 and 30, at discharge and at 4 months. Fatty acid composition of plasma lipid subclasses, RBC and cheek cell phospholipids will be evaluated using TLC for separation and capillary GLC for fatty acid methyl ester identification. Plasma and RBC membrane vitamin E content and RBC osmotic fragility after peroxide exposure will also be measured. The electroretinogram and visual pattern evoked potentials will be used to evaluate visual function in the four groups at 36 weeks post menstrual age and at 4 months adjusted postnatal age. This study should provide useful information on the effects of omega-3 fatty acid deficiency on the developing brain in VLBW infants and may improve early neonatal nutritional practices to optimize later mental development and possibly prevent handicaps.